Articulated mats are used for offshore coastal and marine applications where separation, stabilization, protection and scour prevention is needed for pipelines and other installations submerged and partially submerged, and where shoreline, stream and river erosion protection is needed. These mats are particularly useful in areas where considerable hydrodynamic forces are generated by bottom currents and waves. Thus, for example, a seabed pipeline can be covered with such a mat so that the pipeline is stabilized by the weight of the mat. Examples of articulated mats, their components, and their uses are given in European patent specification 0152232, and U.S. Pat. Nos. 2,876,628; 2,674,856; 4,370,075; 4,357,928; 4,417,828; 5,052,859; and 5,193,937.
The most effective soil covering is concrete because of its high tensile and compressive strength and its almost endless resistance to the action of natural types of water, including slowing the water velocity. Unfortunately, concrete is hard and heavy. To help prevent erosion it may be necessary to raise the elevation of the concrete mat normally used in the art to increase the performance of the mat for high tides, high wave action, tide surges and the like. However, if several inches of rock, concrete or other heavy revetment is placed on a soft shoreline, such as the Louisiana coastal and marsh beaches which in some places are very soft organic soil with vegetation growing in close proximity to the shoreline, the entire height of the material may be settled into the soil.
There is therefore a need in the art for raising the elevation of a concrete mat to increase the performance of the mat to permit the revetment system to function better in high tides, high wave action and tide surges, for example, without adding substantial weight.